Thermostat Wahler or Motorcraft

I used a motorcraft RT-1139 thermostat. Comes with a jiggle valve to help bleed air already installed and cost me 8 bucks. You won’t find any place that says they fit other than some forum posts but they do indeed work, I installed one on my MJ with the only issue being me not refilling the radiator after dumping all the coolant.

I requested they use only Motorcraft thermostat, because I knew there was a part # update. Threw the updated Motorcraft one in and it solved the issue.

Soon as i bought Motorcraft all was normal again

Spend slightly extra and get a quality OEM Wahler thermostat.

Got the Wahler on my 2008/2011 and it was identical to the MB part except the area that had the MB logo on the original one was ground out.

Make sure you use the motorcraft thermostat.

I just replaced the original thermostat at 90,000 miles because at highway speeds it would run slightly cold and took a while to warm up from cold. The new wahler replacement takes just as long and will actually run cold intermittently when not on highway. Occasionally it won’t deviate from center on the highway.

My tstat is wahler. People said that it was better than Mahle. But I found it similarly poor.

I’ve had a Motorcraft thermostat fail after 100mi on my Ford

Thermostat was ALSO replaced when the water pump was, with a Wahler unit. Guess I got 10k miles out of it?